ORIGIN OF SUPERCONDUCTIVITY IN CUPRATE OXIDE - QUANTITATIVE-ANALYSIS ON THE BASIS OF D-P-MODEL

The origin of superconductivity in cuprate oxide systems is studied from the first principle starting with the d-p model Hamiltonian. We derive the Dyson-Gor'kov equations which include the second order terms with respect to Coulomb repulsion U between d-electrons both in normal and anomalous self-energy parts, and solve them completely in due consideration of full momentum and energy structures in the equations. We obtain the superconducting transition temperature T(c) by treating both the attractive interaction and the damping effect on an equal footing. As a result, it is shown that d-wave superconductivity is possible under a suitable condition, though T(c) is suppressed by the damping effect. The possibility of obtaining high T(c) by including higher order terms in U is discussed in connection with the experimental results on TI-systems.